Lecture by Jameel Asghar IT Manager Department of CS&IT NED University of Engineering and Technology, Karachi Functions in C(User defined functions) www.sirjameel.com
What is a function? A function in C language is a block of code that performs a specific task. It has a name and it is reusable i.e. it can be executed from as many different parts in a C Program as required. It also optionally returns a value to the calling program www.sirjameel.com
Properties of C Functions • Every function has a unique name. This name is used to call function from “main()” function. A function can be called from within another function. • A function is independent and it can perform its task without intervention from or interfering with other parts of the program. www.sirjameel.com
Properties of C Functions(cont…) • A function performs a specific task. A task is a distinct job that your program must perform as a part of its overall operation, such as adding two or more integer, sorting an array into numerical order, or calculating a cube root etc. www.sirjameel.com
Properties of C Functions(cont…) • A function returns a value to the calling program. This is optional and depends upon the task your function is going to accomplish. Suppose you want to just show few lines through function then it is not necessary to return a value. But if you are calculating area of rectangle and wanted to use result somewhere in program then you have to send back (return) value to the calling function. www.sirjameel.com
4 Types of functions in C • void function(void) • void function(int) • int function(void) • int function(int) www.sirjameel.com
Type-1 void function(void) www.sirjameel.com
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#include<conio.h> #include<stdio.h> void pakistan(void); void main() { clrscr(); pakistan(); getch(); } void pakistan(void) { printf("I love my Pakistan"); } www.sirjameel.com
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Output I love my Pakistan www.sirjameel.com
We can call a function for more than once in main. www.sirjameel.com
#include<conio.h> #include<stdio.h> void pakistan(void); void main() { clrscr(); pakistan(); pakistan(); getch(); } void pakistan(void) { printf("I love my Pakistan"); } www.sirjameel.com
Output I love my Pakistan I love my Pakistan www.sirjameel.com
We can build/call more than one functions in our program. www.sirjameel.com
#include<conio.h> #include<stdio.h> void pakistan(void); void china(void); void main() { clrscr(); pakistan(); china(); getch(); } void pakistan(void) { printf("I love my Pakistan"); } Void china (void) { printf(“China is Pakistan’s Friend country"); } www.sirjameel.com
Output I love my Pakistan China is Pakistan’s Friend country www.sirjameel.com
Type-2 void function(int) www.sirjameel.com
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#include<conio.h> #include<stdio.h> void square(int); void main() { clrscr(); square(5); getch(); } void square(int x) { printf("Square is %d",x*x); } www.sirjameel.com
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Output Square is 25 www.sirjameel.com
#include<conio.h> #include<stdio.h> void table(int); void main() { clrscr(); table(5); getch(); } void table(int x) { for(int a=1;a<=10;a++) printf("%d*%d=%d\n",a,x,a*x); } www.sirjameel.com
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Output 1*5=5 2*5=10 3*5=15 4*5=20 5*5=25 6*5=30 7*5=35 8*5=40 9*5=45 10*5=50 www.sirjameel.com
We can pass more than one arguments to a function, each can have different type/same type. www.sirjameel.com
#include<conio.h> #include<stdio.h> void add(int, int); void main() { clrscr(); add(5, 7); getch(); } void add(int x, int y) { printf(“Addition is %d",x+y); } www.sirjameel.com
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Output Addition is 12 www.sirjameel.com
Write a program to generate a loop between two numbers.(Use functions to achieve the task) www.sirjameel.com
#include<conio.h> #include<stdio.h> Void makeloop(int, int); void main() { clrscr(); makeloop (2, 15); getch(); } void makeloop (int x, int y) { for(int a=x; a<=y; a++) printf(“%d,”, a); } www.sirjameel.com
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Output 2,3,4,5,6,7,8,9,10,11,12,13,14,15 www.sirjameel.com
Edit same program, get two numbers input from user, then make a loop between these numbers. Ex: Plzz input two numbers: 5 20 5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20 www.sirjameel.com
#include<conio.h> #include<stdio.h> Void makeloop(int, int); void main() { clrscr(); int start, end printf(“Plzz input two numbers:”); scanf(“%d%d”, start, end); makeloop (start, end); getch(); } void makeloop (int x, int y) { for(int a=x; a<=y; a++) printf(“%d,”, a); } www.sirjameel.com
Type-3 int function(void) www.sirjameel.com
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#include<conio.h> #include<stdio.h> int sum(void); void main() { clrscr(); int a; a=sum(); printf(“Sum is %d”, a); getch(); } int sum(void) { int x=2, y=3, z; z=x+y; return(z); } www.sirjameel.com
#include<conio.h> #include<stdio.h> int sum(void); void main() { clrscr(); int a; a=sum(); printf(“Sum is %d”, a); getch(); } int sum(void) { int x=2, y=3, z; z=x+y; return(z); } www.sirjameel.com
Return Keyword • In functions, where we return any value, we usually use a keyword “return”, and the value, which is to be returned is written inside braces, shown after return. • Example: return(z); • The above statement will pass the value of z to the left side variable of calling function. • ie: a=sum(); • Hence the value in z, which is 5 in our program is passed to a. www.sirjameel.com
Type-4 Returns a value. int function(int) Passes the argument(s). www.sirjameel.com
#include<conio.h> #include<stdio.h> int sum(void); void main() { clrscr(); int a; a=sum(2,3); printf(“Sum is %d”, a); getch(); } int sum(int x, int y) { z=x+y; return(z); } www.sirjameel.com
#include<conio.h> #include<stdio.h> int sum(int, int); void main() { clrscr(); int a; a=sum(2,3); printf(“Sum is %d”, a); getch(); } int sum(int x, int y) { z=x+y; return(z); } www.sirjameel.com
